Spray coating methods

ABSTRACT

A method of externally coating select portions of a cylindrical surface with spray material wherein the surface is positioned adjacent to the spray nozzle and at least one mask which is shifted in close proximity to the surface in the vicinity of the nozzle and the surface and mask are rotated while material is applied from the nozzle.

United States Patent [72] inventor Johannes Kiwiet Riverside, Ill.

[2 l Appl. No. 869,435

[22] Filed Sept. 18, 1969 [23] Division of Ser. No. 587,333, Oct. 17, 1966,

Pat. No. 3,532,072

[45] Patented Nov. 2, 1971 [73] Assignee Inland Steel Company Chicago, Ill.

[S4] SPRAY COATING METHODS 3 Claims, 10 Drawing Figs.

[52] 0.8. CI 117/38, 117/43, 1 l7/l05.3, ll7/l05.4, 117/94 [5 1] Int. Cl 844d l/52, B05b 13/02 [50] Field oiSearch ll7/38,43,

References Cited UNITED STATES PATENTS 6/1943 McDougal 2/l955 Williams.... l/l959 Kozak.... 7/1960 Petro 5/l966 Blank et al Primary Examiner-Alfred L. Leavitt Assistant Examiner-M. F. Esposito Attorney-Wolfe, Hubbard, Leydig, Voit & Osann l l7/38 l l8/30l 1 18/301 ABSTRACT: A method of externally coating select portions of a cylindrical surface with spray material wherein the surface is positioned adjacent to the spray nozzle and at least one mask which is shifted in close proximity to the surface in the vicinity of the nozzle and the surface and mask are rotated while material is applied from the nozzle.

PATENTED nuvz I97! 531617.339

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SPRAY COATING METHODS This is a division of application Ser. No. 587,333, filed Oct. 17, I966, now Pat. No. 3,532,072.

The present invention relates generally to spray coating methods and apparatus, particularly, to an improved spray coating system for coating portions of external surfaces of workpieces such, merely by way of example, as a cylindrical Y shell which may comprise the sidewall of a container or the like. In its principal aspects, the invention is concerned with improved spray coating methods characterized by their ability to rapidly coat select portions of a workpiece surface with a material such as paint lacquer, rust inhibitor, or other material in a liquid or semiliquid state, yet wherein the coating is applied uniformly within sharp and well-defined limits even where the surface being coated includes irregularities, contours, projections, curls, and the like.

In various industries, such, for example, as the container manufacturing industry, efforts have been made to apply uniform coatings to the surfaces of workpieces, e.g., the cylindrical sidewall of a container, yet wherein the coating can be applied on a mass production basis. Interior and exteriorsurfaces of container sidewalls are conventionally coated separately often utilizing different coating materials. Rapid handling of shells for coating is troublesome and difficult and some areas present even greater problems in coating such as for example, about the curl formed on the upper edge of a container sidewall. Multimaterial coating, striping and the like have also heretofore presented additional difficulties in han dling and were not readily susceptible to rapid mass production operations. While there is disclosed and claimed in my copending application Ser. No. 492,682 filed Oct. 4, I965, now Pat. No. 3,455,728 and assigned to the assignee of the present invention, centrifugal spray coating methods and apparatus for uniformly coating the internal surface of a cylindrical shell, prior to the present invention, there has not been a completely satisfactory solution to the problem of applying coatings to select portions of the external surface of the workpiece within sharp and well defined limits.

Accordingly, it is a general aim of the present invention to provide an improved spray coating system characterized by its ability to rapidly apply a coating of spray material to select portions of the external surface of the workpiece to be coated. While not so limited in its application, the invention will find especially advantageous use in applying a uniform coating about a curl formed on an edge of a cylindrical shell, such, merely by way of example, as the cylindrical sidewall of a 55- gallon shipping drum of the type commonly made from sheet steel or other suitable material.

In accordance with another of the important aspects of the present invention, it is an object to provide improved methods for spray coating portions of the external surface of a cylindrical shell characterized by their versatility and which readily permit effective use thereof in multimaterial coating, striping and the like, yet wherein the coatings are applied in rapid, continuous operations. In this connection, it is an object to provide a reliable external work surface coating system particularly suitable for mass production operations.

Other objects and advantages of the invention will become apparent as the following description proceeds, taken in conjunction with the accompanying drawings, in which:

FIG. I is a fragmentary, and partially diagrammatic, elevation view of an exemplary material spray system for applying coatings to external portions of a cylindrical shell, such system embodying the features of the present invention:

FIG. 2 is a top plan view of the exemplary spray coating ap- Paratus shown in FIG. 1;

FIG. 3 is an enlarged fragmentary elevation view, partly in section, of a spray coating apparatus used in conjunction with the spray system of the present invention, here illustrating the device in readiness for receiving a cylindrical shell;

FIG. 4 is a fragmentary elevation view partly in section of a portion of the apparatus shown in FIG. 3, here depicting the shell held in position by the apparatus in readiness for the coating operation;

FIG. 5 is an enlarged fragmentary cross section view taken substantially along the line 5-5 in FIG. 3, here depicting the rotatable clamping arrangement for holding the workpiece during the coating operation;

FIG. 6 is an enlarged, cross section view taken substantially along the line 6-6 in FIG. 4;

FIG. 7 is an enlarged fragmentary cross section view taken with a portion of the upper mask cut away for purposes of depicting the interior along the line 7-7 in FIG. 4;

FIG. 8 is an enlarged fragmentary section of the exemplary apparatus of FIG. 1, depicting the spraying of a curl on the upper edge of a cylindrical shell, and illustrating the upper and lower masks for limiting the application of the coating within desired limits; H

FIG. 9 is an enlarged fragmentary view in section taken with a portion of the upper mask cut away for purposes of depicting the interior along the line9--9 in FIG. 7, here illustrating the scraper arrangement for removing excess spray material from the upper mask; and,

FIG. 10 is a fragmentary front end view, similar toI-IG. 4, here depicting a slightly modified spray coating apparatus also embodying the features of the present invention.

While the invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by way of example in thedrawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular-forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as expressed in the appended claims.

Referring now to the drawings, there is diagrammatically illustrated in FIG. 1 an exemplary spray coating system generally indicated at 20, which is particularly suitable for coating select portions of the external surface of cylindrical shells, 21, 22 on a mass production basis and in accordance with the present invention. While the particular type of workpiece to be coated is not critical to the present invention, it will be appreciated as the ensuing description proceeds, that the exemplary spray coating system 20 shown in FIG. 1 will find particularly advantageous, but by no means exclusive, use in coating portions of the external surface of a cylindrical shell such as the sidewalls of conventional SS-gallon shipping containers which can be made of sheet metal or any other suitable natural or synthetic sheet material.

As here illustrated, cylindrical shells 21, 22 are fed to the spray coating station, generally indicated at 24 in seriatim order, by means of a conveyor belt 26 or the like. The particular means for driving the conveyor belt are not critical to the present invention, and may take any of a wide variety of conventional forms well known to those skilled in the art. It should suffice to say that the drive system for the conveyor belt is such that control means are provided for automatically moving the belt to transfer shells from work stationto work station, and for intermittently stopping the belt as successive shells reach a work station so as to permit performance of an operational cycle. In the present instance, in order to insure that the shells, 21, 22 are properly aligned with work station 24, for example, the belt is provided with a plurality of posi tioning lugs 28 which serve to accurately position the shells at predetermined points on the conveyor belt 26.

For the purpose of axially moving the cylindrical shell 21 into the illustrative spray coating station 24, there is provided a pair of oppositely facing C-shaped brackets 30 which are respectively disposed on either side of the conveyor belt 26. Each of the C-shaped brackets 30 includes a pair of upright posts 32 having annular flanges 34 formed adjacent the upper ends thereof, such flanges normally being disposed at the level of or slightly below the level of the upper surface of the belt 26. The arrangement is such that when the belt 26 is stopped with a cylindrical shell accurately positioned beneath the coating station 24, the lower peripheral edge 36 of the shell is disposed immediately above the two pairs of flanges 34. As

shown in FIG. 1, the brackets 30 are coupled to a roller follower member 38 the latter raising and lowering shell 21 under the guidance ofa disc cam 40. The disc cam 40 is fixed to a generally horizontally extending drive shaft 42, driven by motor 44 through roller chain and sprocket drive 46.

The exemplary spray apparatus 20, as shown in FIG. 1, is supported above shells 21, 22 carried by belt 26 on a generally rectangular framework 50 including spaced horizontally extending members 51 and spaced vertically extending columns 52.

For the purpose of distributing liquid or semiliquid spray material on the surface of the workpiece to be coated, the exemplary apparatus includes spray nozzles 54, 55 adjustably mounted respectively to horizontally extending support shafts 56, 57 which are in turn connected to vertically extending support shafts 58, 59 (FIG. 2) through slide clamps 60, 61. The vertical support shafls 58, 59 are connected to a slide clamp 64 fixed to a cross member 51, outboard of the apparatus. The arrangement is such that the spray material, which is normally maintained in a supply reservoir (not shown) is delivered under pressure by means of one or more pumps (not shown), through spray nozzles 54, 55, the latter here being completely ad justablysupported in the work station 24.

In order to confine both airborne particles of spray material emanating from the spray nozzles and drippings from excess spray material carried away from the apparatus, there is provided a rectangular enclosure 66 surrounding the work station. Exhaust vents 68 disposed at the top of the enclosure 66 are connected to a suitable exhaust fan and filter system (not shown) to remove the airborne spray particles and fumes from within the enclosure. A drain 69 at the bottom of the enclosure 66 receives drippings and settled particles of spray material which may be returned to the material source, or discarded, as desired.

In accordance with the present invention, provision is made for receiving the workpiece in the work station 24, rotatably supporting the workpiece within the work station enclosure and rotating the workpiece at a preselected position relative to the path of spray material projected outwardly from the spray nozzles so as to apply a coating to a selected portion of the work surface. To this end, a powerhead, generally indicated at 70 (FIGS. 1 and 3), extends vertically along the center of the work station 24 supported by a pair of crossmembers 72 of frame 50.

As best shown by reference to FIG. 3, the powerhead 70 includes a stationary outer sleeve 74 bolted to a frame members 72 through collar members 76. Disposed within the stationary sleeve 74 and supported with a suitable thrust bearing 78 is a rotatable sleeve member 80 which is rotatably driven by a belt and pulley arrangement 82 through motor drive mechanism 83 (FIG. I). Centrally supported within the rotatable sleeve 80 is an axially shiftable and rotatably supported shaft 86.

In keeping with the invention, the powerhead 70 includes provision for positively clamping the workpiece for rotation with rotatable sleeve 80. As best shown by reference to FIGS. 3, 4, and 5, conjointly, a plurality of expanding shoes, generally indicated at 84, extend radially outward from a spider member 86, the latter being secured to a flanged hub member threadably connected to rotatable sleeve 80 as indicated at 90 (FIGS. 3 and 4). As here shown, (FIG. 5) the clamping shoes 84 are generally T-shaped and have a pair of spaced axially extending bores 88 which receive pins 89 extending radially outward from the spider member 86.

For the purpose of normally urging the clamping shoes 84 radially inward towards their nonexpanded position, compression springs 92 or the like surrounding the outer ends of pins 89 are carried in an enlarged cavity portion of bores 88 so that the springs are confined between a shoulder portion 94 on clamping shoes 84 and retaining members 96 secured to the ends of pins 89. Thus, the springs 92 tend to normally bias the clamping shoes 84 radially inward and, when expanded, the clamping shoes are cammed radially outward against the biasing effect of the springs 92.

For the purpose of properly positioning a shell 21 about the clamping shoes 84, there are provided a plurality of stop fingers 98 (FIGS. 3 and 5) pivotally mounted at the ends of arms 100 on spider member 86. As viewed in FIG. 3, the shell is raised until its upper peripheral edge engages abutment shoulders 100 on stop fingers 98. For the purpose of retracting the stop fingers after the workpiece has been properly positioned, guide pins 101 projecting horizontally from the stop fingers ride in generally L-shaped camming slots 102 formed in plates 104.

In carrying out the present invention, provision is made for camming the clamping shoes 84 radially outward and retracting the stop fingers 98 after the workpiece has been moved into a proper position with respect thereto. To accomplish this, a support plate 106 (FIGS. 3, 4, and 6), mounted below spider member 84 and secured to central shaft 86 of powerhead 70 through suitable support member 107, carries a plurality of upstanding camming members 108 which serve to define outwardly facing cam surfaces 109. The camming members 108 extend through slots 110 provided in clamping shoes 84 and to facilitate relative movement between camming members 108 and clamping shoes 84 for camming the latter radially outward, rollers 112 mounted on the shoes 84 engage the outwardly facing cam surfaces 109 of camming members 108. Suitable adjusting screws 116 (FIG. 6) are provided to regulate the position of the camming members thereby enabling alignment of the expansion of each of the expanding shoes 84.

Plate members 104 which include the guide slot 102 that receives guide pins I01 of stop fingers 98 are also secured to support plate 106. Thus, when the support plate I06 together with the central shaft 86 is shifted downwardly, the cam surfaces 109 of members 108 and rollers 112 on clamping shoes 84 coact to cam the clamping shoes 84 radially outward and at the same time guide pins 101 of stop fingers 98 ride in slots I06 thereby retracting the stop fingers 98 radially inward, as shown in FIG. 4.

Secured to the underside of support plate 106 is a generally frustoconical-shaped guide plate I13, the generally inwardly tapering sidewalls of which help to guide the shell 21 over the clamping portion of the powerhead 70.

In order to rotatably drive the support plate 106 and its associated central shah 86 together with spider 86 and rotatable sleeve 80, there is provided a vertically oriented drive pin I20 secured to support plate 106 and passing through a suitable opening provided in spider 86. The drive pin I20 also insures that camming members 108 are not torque transmitting members.

In keeping with the invention, provision is made for lowering the support plate 106 thereby expanding the clamping shoes and retracting the stop fingers 98 synchronized with the elevating of the workpiece into work station 24, as previously described.

In the exemplary form of the invention, the upper end of the central shaft 86 is threadably received in an annular carrier member 124 (as best shown in FIG. 3). The carrier member I24 is provided with an annular recess 125 which receives a pair of rollers 126 secured to spaced arms 127 of a yoke member 128. The opposite end of the yoke member 128 includes a roller follower I30 which rides on a disc cam 132, the latter being fixed to a horizontally extending shaft I34 supported at the top of the apparatus (FIGS. 1 and 2).

In order to drive shaft 134, there is provided, as best viewed in FIG. I, a generally vertically extending shaft I36 which interconnects the workpiece lifting drive shalt 42 to shaft I34 through bevel gear couplings 137, 138.

In accordance with another of the important aspects of the present invention, provision is made for restricting the amount of surface sprayed so that only a preselected portion of the workpiece is coated within well-defined limits. In order to achieve this result, as best shown by reference to FIGS. 1,3,4, and 8, conjointly, upper and lower masks 140, I42, respectively, are provided to permit spray material from nozzles 54,

55 to be applied to the surface of the workpiece between the masks and prevent application of spray material to other portions of the workpiece.

The upper mask H40 which is of generally dish-shapedconstruction surrounds the powerhead 7d and an arrangement is made so that the upper mask R40 is rotatably driven and axially shifted together with support plnte M6.

Referring to FIGS. 3, 4, and 8, conjointly, the upper mask 140 is secured to the top of an annular flange 143 formed on sleeve member M4 surrounding powerhead 70, while an annular guard member M6 is secured to the lower end of flange 143. Camming plates 104 are secured to the underside of guard member 146 by welding or the like so that guard member 146, sleeve 144 and the upper mask l w'are all positively connected to the support member 106 through camming plates 104.

For the purpose of shielding the internal surface of the workpiece and the lower members of the powerhead from accumulated overflow and dripping of spray material, particularly from the upper mask 140, the guard member 146 is provided with upstanding annular projections or baffles 150 which serve to confine the excess spray material on the top surface of the guard member. A screen 152 carried on the top surface of the guard member provides additional aid in contining excess accumulated material on the top surface of the guard member.

ln order to prevent a large buildup of spray material on the upper mask a scraper arrangement is provided (best illustrated in FIG. 9) which is adjustably supported on a pin 156 protruding from collar 158 surrounding sleeve member 144. The collar is stationarily secured to the enclosure 66 through anchor bolt 160. The scraper, generally indicated at 162, comprises a generally U-shaped support plate 164 pivotally mounted to a support bracket 165, the latter including a clamp [66 which receives pin 156 of collar 158. The slotted portion 168 of support plate 164 receives an outward end portion of the mask 140 and upper and lower scraper members 170, 171, respectively, mounted on the support plate R64 are spring biased against the upper, lower, and end surfaces of the mask 140 by springs 172.

In order to direct spray material removed from the mask by the scraper 162 there is provided. a troughlike drip tray 176 bolted to the underside of support plate 164 and having a downwardly inclined portion 177 which allows the material to flow away from the work area.

In accordance with yet another of the important features of the present invention, provision is made for shifting the lower mask from its initial concentrically disposed surrounding relationship with respect to the workpiece, when receiving the same, to a position in relatively close proximity to the workpiece external surface in the vicinity of the spray nozzles so that a well-defined limit of spray coverage can be accomplished. To this end, referring to FIGS. 1, 3, and 4, conjointly, the lower mask 142 is carried by a horizontally shiftable slide member 180, the latter being nlideably mounted to frame 50. A relatively large diameter opening 181 is provided in the slide member 180 to allow the workpiece to pass into the work station 24, surrounded by enclosure 66, which is secured to slide member 180.

As best shown by reference to FIGS. 3 and 4, it will be observed that the mask 142 includes a main support ring 34 having a generally frustoconical-shaped, upstanding sleeve 185 about its inner peripheral edge l and a generally frustoconical-shaped depending sleeve member 186 about its outer peripheral edge 18%. The mask 142 is concentrically supported with respect to the opening in slide member 180 so that a cylindrical workpiece, brought into the workstation passes through both the opening 181 of slide member 180 and the central opening 187 of mask M2 to position the workpiece about the powerhead 70.

In order to shift the lower mask 142 from its initial concentrically disposed position with respect to the workpiece, as shown in FIG. 3, to a position wherein the upper peripheral edge of sleeve member 185 is in relatively close proximity to the workpiece external surface in the vicinity of the spray nozzle, as shown in MG. 4, provision is made for moving the slide member m0 coupled with the workpiece elevating and powerhead descent and expansion apparatus. To this end, referring to FIGS. 1 and 2, a horizontally extending link W0 journaled at one end to slide member is coupled to vertically extending link 1% through toggle linkage I93. Secured to the cantilever 194 is a follower member 1% which engages a cam disc 1%, the latter being secured to drive shaft 134.

Cam discs 40), M2, and 1196 are profiled and so arranged that rotation of their respective drive shafts 42, B34. in sequence, raises the workpiece into work station 24, lowers powerhead 70 to clamp the workpiece thereto and shifts the slide member carrying the lower mask 142 to the right, as viewed in FIG. 1. Continued rotation of shaft 42 reverses the sequence of operation, first shifting the slide member 130 and mask 142 to a centered position with respect to the workpiece, raising the powerhead to release the clamping members and lowering of the workpiece back on to the conveyor 26.

in accordance with yet another aspect of the present invention, provision is made for rotating the mask 142 with respect to the workpiece and at a sufficient angular velocity to centrifugally carry accumulated spray material away from the inner peripheral edge of the mask. To accomplish this, referring to H68. 1, 3, and 4, conjointly, main support ring 184 of mask 1142 is bolted or otherwise secured to a circular racks member 198 through removable bolts 200 or the like.

For the purpose of driving the circular rack H98, there is provided a pinion 202 fixed to shaft 204 which is rotatably journaled in slide member 180. A pulley 206 fixed to the lower end of shaft 204 beneath slide member 180 receives a belt 208 rotatably driven by pulley 209 of mask drive motor 210, the latter being mounted on slide member 180, in order to support the mask 142 for rotation with respect to the slide member 180 and the workpiece, a plurality of spool members 212 are rotatably journaled to slide member 180 and located about the periphery of circular rack 198 to supportingly receive the same, yet permitting relative rotation between the circular rack and the spools in the preferred form of the invention, the mask 142 is shifted so that a gap of approximately one-eighth inch is main tained between the workpiece and the inner peripheral edge of the mask in the vicinity of the spray nozzles to insure proper separation between the area to which the coating is being applied and the remaining surface area of the workpiece. Also, advantageous results are obtained when the mask 142 is rotated at approximately l00 rpm. to centrifugally carry excess spray material away from the inner peripheral edge of the mask. While those skilled in the art will appreciate that the present invention is not limited to any particular gap dimension or speed of mask rotation, they are presented, merely by way of example, and may vary, dependent upon the spray material utilized, the configuration of the workpiece being coated and the type of spray nozzles used.

Having in mind the foregoing structural details, a brief description of a typical spray coating operation will serve to facilitate an understanding of the present invention. To this end, reference is first made to FIG. l wherein the apparatus is shown with shell 21 positioned along belt 26 beneath the spray device 20. At the start of the cycle. shell Ell is raised off of the conveyor belt and moved upwardly until the upper peripheral edge 36a of the shell engages stop fingers W on powerhead 70, as illustrated in phantom in FIG. ll. After the shell has been brought into position in work station 24, the powerhead is lowered to urge the clamping shoes radially outward thereby clamping the shell to the powerhead for rotation therewith and bringing mask H40 into position above the central opening of the shell. After this occurs, the mask 142 is shifted to the right (FIGS. 4, 7, and 8) thereby assuming the position wherein the inner peripheral edge of the mask 142 is in close proximity to the shell adjacent the left-hand edge of the latter as viewed in FIGS. 4, 7, and 8 to define a lower limit of spray coverage. When the mask 142 is in position, both the powerhead supporting the shell and the mask 142 are rotated through their respective drive motors 83, 210 and subsequently spray material is delivered to nozzles 54, 55 for distribution onto the surface of the shell between the limits defined by masks 140, 142 (FIG. 8).

In the illustrative embodiment shown in FIG. 8, the apparatus has been shown as used for application of a coating to a curl formed at the upper peripheral edge of the shell 21. Consequently, the arrangement is such that material emanating from spray nozzle 54, to the extent that it is not blocked by mask I40, covers approximately the upper half of the curl while material emanating from spray nozzle 55 covers the lower portion of the curl.

After the shell portion being covered has been completely rotated past the spray noules, a preselected number of times, the latter are deactivated and rotation of both the powerhead 70 and the mask I42 is ceased. The mask I42 is then shifted back to its concentrically disposed position about the shell (FIG. 3) and the powerhead is raised, thereby retracting the clamping shoes to their inward position to release the shell. The shell 21 is then returned to the conveyor belt and the cycle repeats itselffor shell 22 and each subsequent shell positioned along the conveyor belt.

Turning now to FIG. [0, there is shown a slightly modified spray coating apparatus 208 which is quite similar in construction and operation to that shown in FIG. 1. However, in the exemplary apparatus shown in FIG. 10, the construction is such that multicolor coating or striping can be accomplished with a different material or color coating also being uniformly applied within sharp and well-defined limits on the exterior surface of the shell. in this instance, the apparatus includes a powerhead 70B, masks 140B, 142 B, slide member I808 and enclosure 668, all similar to those shown in FIG. I.

In carrying out this form of the invention, provision is made for applying a band of differing material or different colored material intermediate the upper and lower peripheral edges of shells in a rapid and continuous manner. To this end, a second rotatable and transversely shiftable mask 242 is carried by slide member 1808 in an axially spaced relation with respect to mask 1428. For the purpose of distributing spray material on the surface of the workpiece intermediate the masks a spray nozzle 246 is provided projecting horizontally into the enclosure 668 between the masks 142B, 242.

In the present exemplary form of the invention, the mask 242 includes a circular rack member 248 and an annular material guard member 250 removably secured to the rack by bolts 252. The guard member 250 which may be of unitary construction, includes a generally horizontally extending portion 250A and a generally upstanding frustoconlcal-shaped portion 2508, the latter portion being in surrounding relationship to a shell supported on the powerhead 70B.

ln order to confine material drippings and excess material moving outwardly along the surface of mask 242 due to centrifugal action, there are provided a plurality of projections or baffles 254 on the top surface of the horizontal portion 250A.

For the purpose of receiving any material overflow from the top surface of the mask horizontal portion 250A, an annular trough 256 surrounds the outer peripheral edge of the guard member 250 and is located slightly below the guard member so that material flowing over the extreme outer baffle member 254 will fall into the trough 256. A suitable drain 258 is provided in the trough which may, if desired, be connected to the source ofmaterial for reuse thereof.

In order to support the mask 250 on slide member 1808 and to rotate the mask 250 in a manner substantially similar to that used in conjunction with mask 142B, shaft 2048 which carries pinion 2025 for driving mask 1428 and shafts 260 which carry support spools 2128 are extended in length and also carry, respectively, a drive pinion 262 and spools 264 for driving and supporting rack 248 of mask 242. Pinion shaft 2048 is rotatably journaled in slide member 1808 with the lower end portion of the shaft extending below the slide member connected to pulley 206B driven by belt 2088 in a manner similar to that described with respect to FIG. I.

For the purpose of defining an upper limit of spray coverage from nozzle 246 and to prevent spray material from being applied to the undersurface portions of the mask 1428, there is provided an annular shield 266 secured to the rack 1988 of mask 1428.

It will, of course, be understood to those skilled in the art that certain of the features and advantages of the present form of the invention may be utilized in a more simplified arrangement for coating a portion of the cylindrical shell surface. Where such usage is desired, and, for example, a curl is not to be coated, but the band or strip is to be applied, then mask 1408 and the upper portion of mask 1428 could be omitted and the apparatus may merely be provided with at least mask 250 and shield portion 266 of mask 1428, without departing from the present invention. In addition, a plurality of pairs of masks could be carried on slide member 1808 with spray nozzles located between respective pairs of masks for applying alternate bands of different color material or the like and the masks can be adjustably mounted to vary the spacing therebetween to enable the application of coatings having varied widths to the shell surface.

It will be apparent from the foregoing that there has herein been disclosed and described in detail novel spray coating systems employing methods which, although characterized by their simplicity and reliability, serve to insure rapid and continuous application of a coating to select portions of a workpiece within well-defined limits. Not only does the novel arrangement of a powerhead and rotating masks contribute to such coating ability, but, moreover, there has herein been disclosed improved methods for applying spray particles to portions of a workpiece surface whereby the coating is applied uniformly within sharp and well-defined limits even where the surface being coated includes irregularities, contours, projections and the like, yet wherein such coating can be applied in a continuous, mass production manner.

I claim as my invention:

1. The method of externally coating a select portion of a cylindrical surface comprising the steps of positioning said portion of the surface adjacent a spray nozzle and at least one mask surrounding the surface for defining an axial limit to said surface portion to be coated, relatively shifting the mask transversely with respect to the surface so that the inner peripheral edge of mask in the vicinity of the spray nozzle is in close proximity to the surface and independently rotating the surface and the mask with respect to one another while applying spray material to said portion from the nozzle, said mask being rotated at a sufficient angular velocity to centrifugally carry accumulated spray material away from the inner peripheral edge ofthe mask.

2. The method of externally coating a select portion of a cylindrical surface comprising the steps of positioning said portion of the surface adjacent a spray nozzle and at least one mask concentric with and surrounding the surface for defining a limit to said surface portion to be coated, shifting the mask transversely with respect to the surface so that the inner peripheral edge of the mask in the vicinity of the spray nozzle is in close proximity to the surface, and independently rotating the surface and the mask with respect to one another while applying spray material to said portion from the nozzle, said mask rotation being such that spray material collecting on the mask is centrifugally carried away from the inner peripheral edge thereof.

3. The method of externally coating select surface portions of cylindrical shells comprising the steps of conveying said shells to a preselected position in seriatim order, moving the first shell from said position into a work station with said surface portion being adjacent to a spray nozzle and at least one mask concentric with and surrounding the surface for defining a limit to said surface portion to be coated, shifting said mask transversely with respect to the surface so that the inner peripheral edge of mask in the vicinity of the spray nozzle is in close proximity to the surface, independently rotating said surface and the mask while applying spray material to said portion from the nozzle, said mask rotation being at a sufiicient angular velocity to centrifugally carry accumulated material away from said inner peripheral edge, returning said first shell to said position after completion of the coating operation, advancing said shell out of said position and conveying a second shell to said position. 

2. The method of externally coating a select portion of a cylindrical surface comprising the steps of positioning said portion of the surface adjacent a spray nozzle and at least one mask concentric with and surrounding the surface for defining a limit to said surface portion to be coated, shifting the mask transversely with respect to the surface so that the inner peripheral edge of the mask in the vicinity of the spray nozzle is in close proximity to the surface, and independently rotating the surface and the mask with respect to one another while applying spray material to said portion from the nozzle, said mask rotation being such that spray material collecting on the mask is centrifugally carried away from the inner peripheral edge thereof.
 3. The method of externally coating select surface portions of cylindrical shells comprising the steps of conveying said shells to a preselected position in seriatim order, moving the first shell from said position into a work station with said surface portion being adjacent to a spray nozzle and at least one mask concentric with and surrounding the surface for defining a limit to said surface portion to be coated, shifting said mask transversely with respect to the surface so that the inner peripheral edge of mask in the vicinity of the spray nozzle is in close proximity to the surface, independently rotating said surface and the mask while applying spray material to said portion from the nozzle, said mask rotation being at a sufficient angular velocity to centrifugally carry accumulated material away from said inner peripheral edge, returning said first shell to said position after completion of the coating operation, advancing said shell out of said position and conveying a second shell to said position. 